The invention relates to a radiation-sensitive composition containing esters of (1,2-naphthoquinone 2-diazide)-4- and/or -5-sulfonic acid with at least two different hydroxybenzophenones and a radiation-sensitive recording material prepared therewith.
Important stages in the production of electronic components are the imagewise exposure and the following development of radiation-sensitive layers applied to the material which is to be provided with a pattern.
Suitable radiation-sensitive layers generally contain a resinous binder which is insoluble in water and soluble or at least swellable in aqueous alkaline solutions and at least one radiation-sensitive compound and, if appropriate, further additives. The photoactive components used in positive-working layers are in most cases derivatives of 1,2-naphthoquinone 2-diazides.
A plurality of derivatives of this type, e.g., esters of (1,2-naphthoquinone 2-diazide)-sulfonic acids with aromatic hydroxyl compounds, are known in the art and are employed as radiation-sensitive components in positive-working recording materials. In his book "Light-Sensitive Systems," published by John Wiley & Sons, New York, 1965, pages 343 to 351, Jaromir Kosar has described a number of radiation-sensitive naphthoquinone diazides.
The esters of (naphthoquinone diazide)-sulfonic acids with polyhydroxylated benzophenones, in particular with 2,3,4-trihydroxybenzophenone and with 2,3,4,4'-tetrahydroxybenzophenone are customarily used and have been described in many publications.
The advancing miniaturization of electronic components requires the production of progressively smaller patterns. Radiation-sensitive layers, so-called "photoresists", are therefore required, which have an increasingly higher resolving power. It is known that the resolving power can be improved by increasing the diazoquinone content in the radiation-sensitive layer (H. Muenzel, J. Lux, R. Schulz, "A- and B-Parameter Dependent Submicron Stepper Performance of Positive Type Photoresist," Microelectronic Engineering 6, 1987, pages 421 to 426). It is moreover known that polyfunctional diazonaphthoquinones can enhance contrast and resolution in photoresists (P. Trefonas III, B. K. Daniels, "New Principle for Image Enhancement in Single Layer Positive Photoresists," Proceedings of SPIE, 771, 1987, pages 194 to 210).
Polyfunctional diazonaphthoquinones which are excellently suitable for use as radiation-sensitive components in positive-working photoresists comprise the tetraesters of (1,2-naphthoquinone 2-diazide)-4- and -5-sulfonic acid with 2,3,4,4'-tetrahydroxybenzophenone. However, since these compounds have a relatively low solubility, the concentration thereof in the radiation-sensitive compositions can only be increased to a degree which is insufficient to obtain an improved resolving power.
Depending upon the degree of esterification, 2,3,4,4'-tetrahydroxybenzophenone which is not completely esterified with naphthoquinone diazide sulfonic acid may also be a suitable radiation-sensitive component for positive-working photoresists, but the storage stability of these photoresists is very limited.
JP-A 01-222255, 01-49038 (1989) and 63-249143 (1988) have already described measures to obviate these disadvantages. According to these publications, the storage stability of resists was improved, either by a special purification of the radiation-sensitive component or by using dimethyl formamide as a solvent. It is, however, desirable to prevent expensive purification treatments and use only solvents whose physical characteristics (boiling point, etc.) do not impair the lithographic properties of the resists and which are absolutely non-toxic.